Analytical apparatus



Nov. 14, 1944. G. M. DREHER ANALYTICAL APPARATUS Filed April 18, 1942 2 Sheets-Sheet l FIG.

. z jwfl MM QiENTOR Nov. 14, 1944. 6. M. DREHER r 2,362,687

ANALYTICAL APPARATUS Filed April 18, 1942 2 Sheets-Sheet 2 n1, II l l/llI l/I/l (1,11,10,11

Patented Nov. 14, 1944 umrso STATESPATENT orrics ANALYTICAL APPARATUS George Miller Dreher, Grosse Pointe Woods, Mich.

Application April 18, 1942, Serial No. 439,453

3 Claims.

My invention relates to high temperature analytical apparatus for use in determining more particularly the sulfur and carbon content of steel and iron.

One of the objects of my invention is to pro,- vide a special construction of combustion furnace by which a very high temperature is applied to a relatively small portion of the length of a combustion tube. This reduction in length reduces volume of tube which reduces volume of gases to be measured. This shortens time of analysis which is an important element in the manufacture of steel and iron.

Another object of this invention is the provision of a special construction of combustion tube and a removable filter tube located in hot zone of combustion tube, to collect the oxides of iron which are formed during combustion and thus preventing same from collecting in cold end of combustion tube and acting as a catalyst in converting sulfur dioxide into sulfur trioxide which also collects in cold end of tube and prevents full sulfur content of steel or iron being measured in absorption chamber. A still further object of this invention is the provision of a combustion tube having its bore enlarged in hot zone above combustion boat for collection of spattering slags directly above boat during rapid combustion of sample and thus increasing life of tube.

I attain the above and other objects by the construction hereafter described in detail and shown in the accompanying drawings, in Which-.-

Figure 1 is a side elevation of combustion furnace. Figure 2 is a top plan view of furnace.

Figure 3 is a section on line 33 of Figure 2.

Figure 4 is a vertical longitudinal sectional view of a combustion tube and a filter liner. Figure 5 is a sectional View of a modification of construction shown in Figure 4. Figure 6 is a side view of another type of combustion tube.

The same reference numerals designate the same parts in the different views. Numeral I designates combustion furnace provided with combustion chamber 2 shown in dotted outline in Figures 1, 2, 4, 5 and 6. The chamber 2 is provided with walls 3 of any suitable heat insulating refractory material, as fire brick. Passing through the combustion chamber 2 and also the front, and rear walls of furnace are two combustion tubes}. Tubes 4 project a considerable distance beyond outside walls of the furnace so that the ends of tubes 4 are at some distance from heat of furnace to permit use of tight fitting connections, as rubber stopper 5 and rubber hose 6,

or other fitting, the stopper 5 being removable for insertion of boat 1 containing sample to be burned and also perforated for insertion of tube 8 to oxygen supply, the hose 6, or other fitting, leading to apparatus for determining carbon and sulfur content of sample.

Heating elements 9 extend through combustion chamber 2 and transversely of combustion tubes 4. Said elements 9 also extend through side walls of furnace to the exterior of the furnace on the opposite sides thereof as shown in Figures 2 and 3. -These heating elements 9 are composed of silicon carbide, but instead of being composed of silicon carbide for their entire length are prefer ably of silicon carbide for approximately only that portion which is in combustion chamber 2 or that portion which is in combustion chamber and for some distance in side walls. The terminals of heating elements 9 which are integral with the central silicon carbide portion extend beyond the furnace side walls where electrical contact is made with finger clips I0 attached to electrical conductors. These heating elements are known in the trade as globars and operate at a continuous temperature of 2500 degrees centigrade or intermittently at a temperature of 2650 degrees centigrade.

These silicon carbide heating elements'because of the above high temperatures attained give more accurate and quicker carbon and sulfur determinations. By disposing elements 9 transversely of combustion tubes 4 as above described the intense heat above referred to may be con fined to a shorter length of a combustion tube 4 than if said heating elements Were disposed parallel to said tube, thus permitting the use of shorter tubes which reduces volumes of gases to be analyzed resulting also in quicker and more accurate chemical determinations which are especially important in volumetric analysis for sulfur dioxide and carbon dioxide from combustion of sample. These quick and accurate determinations as above described would permit the laboratories to keep up with more rapid production or control work as in the manufacture of iron and steel.

The bore of combustion tube 4 is tapering as shown in Figure 4. In this bore is a filter tube l I, also tapered so as to snugly fit bore of tube 4 to prevent any appreciable amount of gas passing between tube 4 and tube H. The small end of tube II is closed by wall l2 which is porous and integral with side walls of tube 4. The tube II including end wall I2 is formed of any suitable porous refractory material as zirconium oxide or aluminum oxide. The combustion boat 1 containing the sample to be analyzed, such as steel, is placed in filter tube II, to be burned by the passage of oxygen over the heated sample. The sulfur content of steel burns to sulfur dioxide which passes through porous end wall of filter tube l i but the iron oxides formed by the burning of the steel are retained within the filter tube I l; otherwise these iron oxides would collect at the relatively cold narrow end of combustion tube A exterior of the furnace. These iron oxides deposited in this cold end cause a portion of the sulfur dioxide to be deposited as sulfur trioxide by the catalytic effect of the iron oxides on the sulfur dioxide thus preventing the entire sulfur content of sample passing to absorption vessel. This filter tube l i also shields combustion tube 4 from spattering iron slags which adhere to walls of filter tube directly above combustion boat I when sample of steel or iron is burned by passage of oxygen over same. After a certain amount of slag has accumulated in filter tube II, the boat 1 can no longer be placed in same, in which event tube ii may be removed and replaced by a new filter tube at a small fraction of the cost of replacement of a new combustion tube 4. An opening !3 through side Wall of tube H permits a suitable implement to engage tube II and remove same.

The construction shown in Figure is similar to that shown in Figure 4 above described, except that combustion tube 4 is provided with an annular shoulder IQ for abutment of an annular rib on filter tube ii; an asbestos Washer l6 being located between said shoulder and rib to form a gas seal.

In the modification shown in Figure 6 the combustion tube 4" is provided with an enlarged space H in the heating zone of tube above combustion boat 1. The slag that spatters during burning of sample of iron or steel in boat adheres to the wall of combustion tube. After use for some time the bore of combustion tube commonly used is clogged with this slag which prevents placing boat in hot zone of tube. By providing bore of tube 4 with enlargement I! the life of tube is greatly prolonged. The bore of tube 4" from enlargement i! to entrance end of tube at stopper 5 may be reduced to a size sufiicient for convenient passage of boat into enlargement II. The bore of tube from enlargement I! to exit end at rubber hose 6 or other fitting is also reduced sufiicient for passage of gases. This reduction in size which reduces volume of tube also reduces volumes of gases to be analyzed. For a similar purpose combustion tubes 4 and 4 are also reduced from approximately heating zone of tube or combustion chamber 2 to exit end at rubber hose 6 or other fitting.

The construction above described may be changed in various ways without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. In analytical apparatus, a combustion furnace having a heating chamber, heat insulating walls surrounding said chamber, a combustion tube of refractory material and integral construction passing through said chamber and extending for a substantial distance beyond the front and also beyond the rear of the furnace to relatively cool zones, said tube at its front end having an opening for insertion of a combustion boat containing the sample to be determined and for also receiving a removable resilient fitting for connection to an oxygen or other gas supply, said tube at its rear exit end being open and adapted to receive a flexible connection for passage of gases from said combustion tube, one set of silicon carbide heating elements disposed above said tube, and another set of silicon carbide heating elements disposed below said tube, the heating elements of each set passing through said heating chamber, and extending transversely of the tube, and spaced along the length of the tube relatively close each other but at substantial distances from the opposite ends of the tube, to permit a relatively short intermediate portion of the tube being intensely heated and the opposite ends of the tube remaining relatively cool.

2. In analytical apparatus, a combustion furnace having a heating chamber, heat insulating walls surrounding said chamber, a combustion tube of refractory material and integral construction passing through said chamber and extending for a substantial distance to the front and also to the rear of furnace into relatively cool-zones, said tube at its front end having an opening for insertion of a combustion boat containing the sample to be determined and for also receiving a removable resilient fitting for connection to an oxygen or other gas supply, said tube at its rear end having an opening for exit of gases from said tube, said tube having an enlarged portion and a reduced portion integral with the enlarged portion, said enlarged portion extending from the front end of the tube to adjacent the rear of the heating chamber, said reduced portion continuing from the enlarged portion to the rear end of the tube, one set of silicon carbide heating elements disposed above said tube, another set of silicon carbide heating elements disposed below said tube, the heating elements of each set passing through said heating chamber, and extending transversely of the tube, and spaced along the length of the tube relatively close to each other but at substantial distances from the opposite ends of the tube to permit a relatively short intermediate portion of the tube being intensely heated and the opposite ends of the tube remaining relatively cool, said intensely heated relatively short intermediate portion being that portion of the enlarged portion adjacent to and immediately forward of said reduced portion of the tube.

3. In analytical apparatus, a combustion furnace having a heating chamber, heat insulating walls surrounding said chamber, a combustion tube of refractory material and integral construction passing through said chamber and extending a substantial distance beyond the front and also beyond the rear of the furnace to relatively cool zones, said tube at its front end having an opening for insertion of a combustion boat containing the sample to be determined, and for also receiving a removable resilient fitting for connection to an oxygen or other gas supply, said tube at its rear exit end being open and adapted to receive a flexible connection for passage of gases from said combustion tube, one set of silicon carbide heating elements disposed on one side of said tube and another set of silicon carbide heating elements disposed on the opposite side of said tube, the heating elements of each set passing through said chamber, and extending transversely of the tube and spaced along the length of tube relatively close each other but at substantial distances from the opposite ends of the tube, to permit a relatively short intermediate portion of the tube being intensely heated and the opposite ends of the tube remaining relatively cool.

GEORGE MILLER DREHER. 

